Under the amendment they introduced last week, firearms purchased at gun shows and over the Internet would require federally licensed gun dealer to conduct a background check.

Potential Republican swing votes have steadily announced their opposition to the Manchin-Toomey proposal, putting pressure on the sponsors to woo Begich and other lawmakers from rural states. Many people in Alaska, the largest state in the nation by geographic area, do not live within hundreds of miles of a licensed gun dealer.